Method of making a self-protected thyristor

Abstract

The present invention is directed to a thyristor self-protected against overvoltage by the avalanche mechanism, the protection resulting from a well cut in the top surface of the thyristor and extending through one base region of the thyristor and forming two regions of opposite conductivity type at the bottom of said well, and to the process for making the thyristor.

We claim as our invention: 
     
       1. A process for making a thyristor, said thyristor being self-protected from overvoltage by the avalanche mechanism, comprising, forming two regions of a second type of conductivity in a body of semiconductor material of a first type of conductivity by diffusing a suitable doping material through a top and a bottom surface of said body, said two regions of second type conductivity being separated by a region of said first type conductivity, forming a well in a central portion of said top surface of said body, said well extending at least entirely through said region of second type conductivity formed by diffusion through said top surface of said body of first type conductivity, said well having a bottom surface, implanting ions, capable of forming a region of first type conductivity, through said bottom surface of said well, whereby a region of said first type of conductivity is formed adjacent to the bottom surface of said well, forming a region of said second type of conductivity between said bottom surface of said well and said region of first type conductivity formed by ion implantation, activating said implanted region, forming at least one region of said first type of conductivity in said region of second type conductivity formed by diffusion through said top surface, said at least one region being spaced apart from said well, said at least one region extending into said region of second type of conductivity to a width less than the width of the region of second type conductivity, affixing metal electrical contacts to said top surface of said body in ohmic electrical contact with said at least one region and said region of second type of conductivity, affixing a second metal electrical contact to the bottom surface of said body in ohmic electrical contact with said region of second type conductivity formed by diffusion through said bottom surface of said body. 
     
     
       2. The process of claim 1 in which the well enters into the region of first type of conductivity that separates the two regions of second type conductivity formed by diffusion through the top and bottom surfaces of the body. 
     
     
       3. The process of claim 1 in which the region of second type conductivity disposed between the bottom surface of said well and the region of first type conductivity formed by ion implantation, is formed by ion implantation. 
     
     
       4. The process of claim 3 in which the well is formed by laser etching.